Method for improving engine fuel efficiency

ABSTRACT

A method for improving fuel efficiency while maintaining or improving deposit control, in an engine lubricated with a lubricating oil. The lubricating engine oil has a composition including from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier, and one or more other lubricating oil additives. The lubricating engine oils are useful in internal combustion engines including direct injection, gasoline and diesel engines.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional Application No. 62/670,099, filed on May 11, 2018 the entire contents of which are incorporated herein by reference.

FIELD

This disclosure relates to improving fuel efficiency while maintaining or improving deposit control, in an engine lubricated with a lubricating oil by including at least one ester based Group V base stock and at least one viscosity modifier in the lubricating oil.

BACKGROUND

Fuel efficiency requirements for passenger vehicles are becoming increasingly more stringent. New legislation in the United States and European Union within the past few years has set fuel economy and emissions targets not readily achievable with today's vehicle and lubricant technology.

The emission test cycle currently used to certify emission performance of new vehicles in Europe is the New European Drive Cycle (NEDC), which consists of measuring the CO₂ emissions or fuel consumption of a vehicle. In the NEDC, a vehicle is tested on a chassis dynamometer. The testing begins at 20-30° C. The vehicle must achieve a specific speed versus time profile, which simulates urban driving and extra-urban driving. The entire testing cycle lasts for 1180 seconds. The NEDC drive cycle in the future will be replaced by the Worldwide Harmonized Light Vehicles Test Procedure (WLTP). Like the NEDC procedure, in the WLTP test, the vehicle begins at 20-30° C. The WLTP speed versus time profile is more dynamic then the NEDC cycle and the test last for 30 minutes. As both of these fuel economy/emission tests begin at 20-30° C., having a lubricant with a lower viscosity in this temperature range is desirable to reduce emissions and improve fuel economy.

To address these increasing standards, automotive original equipment manufacturers are demanding better fuel economy as a lubricant-related performance characteristic, while maintaining deposit control and oxidative stability requirements. One well known way to increase fuel economy is to decrease the viscosity of the lubricating oil. However, this approach is now reaching the limits of current equipment capabilities and specifications. At a given viscosity, it is well known that adding organic or organic metallic friction modifiers reduces the surface friction of the lubricating oil and allows for better fuel economy. However these additives often bring with them detrimental effects such as increased deposit formation, seals impacts, or they out-compete the anti-wear components for limited surface sites, thereby not allowing the formation of an anti-wear film, causing increased wear.

Contemporary lubricants such as engine oils use mixtures of additives such as dispersants, detergents, inhibitors, viscosity index improvers and the like to provide engine cleanliness and durability under a wide range of performance conditions of temperature, pressure, and lubricant service life.

Lubricant-related performance characteristics such as high temperature deposit control and fuel economy are extremely advantageous attributes as measured by a variety of bench and engine tests. As indicated above, it is known that adding organic friction modifiers to a lubricant formulation imparts frictional benefits at low temperatures, consequently improving the lubricant fuel economy performance. At high temperatures, however, adding increased levels of organic friction modifier can invite high temperature performance issues. For example, engine deposits are undesirable consequences of high levels of friction modifier in an engine oil formulation at high temperature engine operation.

A major challenge in engine oil formulation is simultaneously achieving high temperature deposit control while also achieving improved fuel economy.

Despite the advances in lubricant oil formulation technology, there exists a need for an engine oil lubricant that effectively improves fuel economy while maintaining or improving deposit control.

SUMMARY

This disclosure relates in part to a method for improving fuel efficiency, while maintaining or improving deposit control, in an engine lubricated with a lubricating oil by including at least one ester based Group V base stock and at least one viscosity modifier in the lubricating oil. The lubricating oils of this disclosure are useful in internal combustion engines including direct injection, gasoline and diesel engines.

This disclosure also relates in part to a method for improving fuel efficiency while maintaining or improving deposit control, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil. The formulated oil has a composition comprising from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier, and wherein the remainder of the lubricating engine oil includes one or more other lubricating oil additives. The fuel efficiency properties are improved (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and deposit control is maintained or improved (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier.

This disclosure further relates in part to a lubricating engine oil having a composition comprising from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier, and wherein the remainder of the lubricating engine oil includes one or more other lubricating oil additives. The fuel efficiency properties are improved (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and deposit control is maintained or improved (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier.

It has been surprisingly found that, in accordance with this disclosure, improvements in fuel economy are obtained without sacrificing engine cleanliness (e.g., while maintaining or improving deposit control) in an engine lubricated with a lubricating oil, by including at least one ester based Group V base stock and at least one viscosity modifier in the lubricating oil.

Other objects and advantages of the present disclosure will become apparent from the detailed description that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the various base stocks and the properties of the base stocks used in accordance with the embodiments of this disclosure.

FIG. 2 shows inventive and comparative formulations of this disclosure (e.g., various ester based Group V base stocks and viscosity modifiers) in the lubricating oil and the resulting properties (kinematic viscosity, high temperature high shear viscosity, TEOST deposits, Viscosity Index, CCS viscosity and SAE oil viscosity grade) of the oils. Formulation details are shown in weight percent based on the total weight percent of the formulation, of various formulations.

FIG. 3 shows other inventive and comparative formulations of this disclosure (e.g., various ester based Group V base stocks and viscosity modifiers) in the lubricating oil and the resulting properties (kinematic viscosity, high temperature high shear viscosity, TEOST deposits, Viscosity Index, CCS viscosity and SAE oil viscosity grade) of the oils.

FIG. 4 shows still other inventive and comparative formulations of this disclosure (e.g., various ester based Group V base stocks and viscosity modifiers) in the lubricating oil and the resulting properties (kinematic viscosity, high temperature high shear viscosity, TEOST deposits, Viscosity Index, CCS viscosity and SAE oil viscosity grade) of the oils.

FIG. 5 shows still yet other inventive and comparative formulations of this disclosure (e.g., various ester based Group V base stocks and viscosity modifiers) in the lubricating oil and the resulting properties (kinematic viscosity, high temperature high shear viscosity, TEOST deposits, Viscosity Index, CCS viscosity and SAE oil viscosity grade) of the oils.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claims herein are modified by “about” or “approximately” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art. The phrase “major amount” or “major component” as it relates to components included within the lubricating oils of the specification and the claims means greater than or equal to 50 wt. %, or greater than or equal to 60 wt. %, or greater than or equal to 70 wt. %, or greater than or equal to 80 wt. %, or greater than or equal to 90 wt. % based on the total weight of the lubricating oil. The phrase “minor amount” or “minor component” as it relates to components included within the lubricating oils of the specification and the claims means less than 50 wt. %, or less than or equal to 40 wt. %, or less than or equal to 30 wt. %, or greater than or equal to 20 wt. %, or less than or equal to 10 wt. %, or less than or equal to 5 wt. %, or less than or equal to 2 wt. %, or less than or equal to 1 wt. %, based on the total weight of the lubricating oil. The phrase “essentially free” as it relates to components included within the lubricating oils of the specification and the claims means that the particular component is at 0 weight % within the lubricating oil, or alternatively is at impurity type levels within the lubricating oil (less than 100 ppm, or less than 20 ppm, or less than 10 ppm, or less than 1 ppm). The phrase “other lubricating oil additives” as used in the specification and the claims means other lubricating oil additives that are not specifically recited in the particular section of the specification or the claims. For example, other lubricating oil additives may include, but are not limited to, an anti-wear additive, antioxidant, detergents, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, friction modifier and combinations thereof.

It has now been found that improved fuel efficiency can be attained, while deposit control is unexpectedly maintained or improved, in an engine lubricated with a lubricating oil by using as the lubricating oil a formulated oil that has at least one ester based Group V base stock and at least one viscosity modifier in the lubricating oil. The formulated oil preferably comprises a first lubricating oil base stock, a second lubricating oil base stock comprising at least one ester based Group V base stock and at least one viscosity modifier. The lubricating oils of this disclosure are particularly advantageous as passenger vehicle engine oil (PVEO) products.

The lubricating oils of this disclosure provide a low kinematic viscosity at 25 deg. C. as a measure of fuel efficiency improvement and a low TEOST 33C deposits as measure of deposit control improvement. In particular, the lubricating oils of this disclosure provide a novel combination of a kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt and a TEOST 33C total deposits of less than or equal to 60 mg. A lower HTHS viscosity engine oil also generally provides superior fuel economy to a higher HTHS viscosity product.

In one form of the present disclosure, provided is a lubricating engine oil that includes from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier. The remainder of the lubricating engine oil includes one or more other lubricating oil additives. The inventive lubricating engine oil provides improved fuel efficiency properties (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and maintained or improved deposit control (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier. The kinematic viscosity at 25 deg. C. and the TEOST 33C total deposits achieved using the inventive lubricating engine oil are significantly and surprisingly improved compared to lubricating engine oils not containing the at least one ester based Group V base stock and the at least one viscosity modifier.

The one or more other lubricating oil additives constitute the remainder of the formulated oil and are selected from one or more of the following: an anti-wear additive, antioxidant, detergents, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, friction modifier and combinations thereof. These one or more other lubricating oil additives are described in greater detail below.

In another form of the present disclosure, provided is a method for improving fuel efficiency, while maintaining or improving deposit control, in an engine lubricated with a lubricating oil by using as the lubricating engine oil a formulated oil, said formulated oil having a composition including: from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier. The remainder of the lubricating engine oil includes one or more other lubricating oil additives. The inventive lubricating engine oil provides improved fuel efficiency properties (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and maintained or improved deposit control (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier. The kinematic viscosity at 25 deg. C. and the TEOST 33C total deposits achieved using the inventive lubricating engine oil are significantly and surprisingly improved compared to lubricating engine oils not containing the at least one ester based Group V base stock and the at least one viscosity modifier.

The inventive lubricating engine oils described above have a kinematic viscosity, according to ASTM standards, of 8 cSt to 15 cSt (or mm²/s) at 100° C., preferably of 9 cSt to 14 cSt (or mm²/s) at 100° C., more preferably of 10 cSt to 13 cSt (or mm²/s) at 100° C., and even more preferably of 11 cSt to 12 cSt (or mm²/s) at 100° C.

The inventive lubricating engine oils described above have a low temperature kinematic viscosity (25 deg. C.), according to ASTM standards, of less than or equal to 125 cSt at 25° C., or less than or equal to 110 cSt at 25° C., or less than or equal to 100 cSt at 25° C., or less than or equal to 90 cSt at 25° C., or less than or equal to 80 cSt at 25° C., less than or equal to 75 cSt at 25° C. The low temperature kinematic viscosity at 25 deg. C. correlates with improved fuel efficiency with lower values preferred.

The inventive lubricating engine oils described above have a high temperature high shear (HTHS) viscosity at 150° C. as measured by ASTM D4683 that ranges from 1.5 to 4.5 cP, or 1.75 to 4.25 cP, or 2.0 to 4.0 cP, or 2.25 to 3.75 cP, or 2.5 to 3.5 cP, or 2.75 to 3.25 cP.

The inventive lubricating engine oil and the inventive method for improving fuel efficiency and deposit control provide improved deposit control as measured by the TEOST 33C test to yield total deposits less than or equal to 60 mg, or less than or equal to 50 mg, or less than or equal to 40 mg, or less than or equal to 30 mg, or less than or equal to 20 mg, or less than or equal to 10 mg.

The inventive lubricating engine oils described above are particularly suitable as a lubricating engine oil for a passenger vehicle engine oil (PVEO). The inventive lubricating engine oils described above are also particularly suitable as a lubricating engine oil for an SAE viscosity grade motor oil selected from 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.

Lubricating Oil Base Stocks

The lubricating engine oils of the instant disclosure include a combination of a first lubricating oil base stock and a second lubricating oil base stock. The first lubricating oil base stock is selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof. The second lubricating oil base stock includes at least one ester based Group V base stock. Non-limiting exemplary ester based Group V base stocks of the instant disclosure include a monoester, a di-ester, a polyol ester, a complex ester or mixtures thereof derived from a renewable biological material and combinations thereof. The renewable biological material may be derived from coconut oil, palm oil, rapeseed oil, soy oil, vegetable oil, or sunflower oil.

Advantageous ester based Group V base stocks of the instant disclosure include a C8/C10/C12/C14/C16/C18 Estolide ester, a C11/C13/C15/C17 Estolide ester, a C8/C10 trimethyloipropane (IMP) ester, a C6/C7/C8/C10 TMP ester, a C5/C6/C7/C8/C9/C10 TMP ester, a C8/C10/C12/C14/C16/C18/C20 TMP ester, a C7/C8/C10 TMP ester, a C7/C9/C11/C13/C15 TMP ester, a C6/C7/C9 TMP ester, a C6/C7/C9 TMP ester, a C4/C5/C6/C7/C8/C9 TMP ester, a C15/C17 propylene glycol diester, a C16/C18 propylene glycol diester and combinations thereof.

The first lubricating oil base stock constitutes from 20 to 85 wt %, or 25 to 80 wt %, or 30 to 75 wt %, or 35 to 70 wt %, or 40 to 65 wt %, or 45 to 60 wt % of the total weight of the lubricating engine oil. The second lubricating oil base stock constitutes from 5 to 55 wt %, or 10 to 50 wt %, or 15 to 45 wt %, or 20 to 40 wt %, or 25 to 35 wt % of the total weight of the lubricating engine oil. In one advantageous form of the lubricating engine oils disclosed herein, the at least one ester based Group V base stock comprises from 25 to 55 wt % of the total weight of the lubricating engine oil. In another advantageous form of the lubricating engine oils disclosed herein, the first lubricating oil base stock is a combination of a Group III gas to liquids (GTL) base stock and a Group IV polyalphaolefin (PAO) base stock. In an even more advantageous form, the GTL ranges from 20 to 75 wt % of the lubricating engine oil and the PAO ranges from 2 to 10 wt % of the lubricating engine oil. For the Group III GTL base stock and the Group IV PAO base stocks, particularly advantageous viscosity grades are those having a kinematic viscosity at 100 deg. C. of 4 cSt, or 6 cSt, or 8 cSt.

Non-limiting exemplary first and second lubricating oil base stocks and their properties of the instant disclosure are shown in FIG. 1. Further details of the Group I, Group II, Group III, Group IV and ester based Group V base stocks of the instant disclosure are described below.

Lubricating base oils that are useful in the present disclosure are both natural oils, and synthetic oils, and unconventional oils (or mixtures thereof) can be used unrefined, refined, or rerefined (the latter is also known as reclaimed or reprocessed oil). Unrefined oils are those obtained directly from a natural or synthetic source and used without added purification. These include shale oil obtained directly from retorting operations, petroleum oil obtained directly from primary distillation, and ester oil obtained directly from an esterification process. Refined oils are similar to the oils discussed for unrefined oils except refined oils are subjected to one or more purification steps to improve at least one lubricating oil property. One skilled in the art is familiar with many purification processes. These processes include solvent extraction, secondary distillation, acid extraction, base extraction, filtration, and percolation. Rerefined oils are obtained by processes analogous to refined oils but using an oil that has been previously used as a feed stock.

Groups I, II, III, IV and V are broad base oil stock categories developed and defined by the American Petroleum Institute (API Publication 1509; www.API.org) to create guidelines for lubricant base oils. Group I base stocks have a viscosity index of between 80 to 120 and contain greater than 0.03% sulfur and/or less than 90% saturates. Group II base stocks have a viscosity index of between 80 to 120, and contain less than or equal to 0.03% sulfur and greater than or equal to 90% saturates. Group III stocks have a viscosity index greater than 120 and contain less than or equal to 0.03% sulfur and greater than 90% saturates. Group IV includes polyalphaolefins (PAO). Group V base stock includes base stocks not included in Groups I-IV. Table 1 below summarizes properties of each of these five groups.

TABLE 1 Base Oil Properties Saturates Sulfur Viscosity Index Group I   <90 and/or  >0.03% and ≥80 and <120 Group II ≥90 and ≤0.03% and ≥80 and <120 Group III ≥90 and ≤0.03% and ≥120 Group IV Polyalphaolefins (PAO) Group V All other base oil stocks not included in Groups I, II, III or IV

Natural oils include animal oils, vegetable oils (castor oil and lard oil, for example), and mineral oils. Animal and vegetable oils possessing favorable thermal oxidative stability can be used. Of the natural oils, mineral oils are preferred. Mineral oils vary widely as to their crude source, for example, as to whether they are paraffinic, naphthenic, or mixed paraffinic-naphthenic. Oils derived from coal or shale are also useful. Natural oils vary also as to the method used for their production and purification, for example, their distillation range and whether they are straight run or cracked, hydrorefined, or solvent extracted.

Group II and/or Group III hydroprocessed or hydrocracked basestocks, including synthetic oils such as polyalphaolefins, alkyl aromatics and synthetic esters are also well known basestock oils.

Synthetic oils include hydrocarbon oil. Hydrocarbon oils include oils such as polymerized and interpolymerized olefins (polybutylenes, polypropylenes, propylene isobutylene copolymers, ethylene-olefin copolymers, and ethylene-alphaolefin copolymers, for example). Polyalphaolefin (PAO) oil base stocks are commonly used synthetic hydrocarbon oil. By way of example, PAOs derived from C₆, C₈, C₁₀, C₁₂, C₁₄ olefins or mixtures thereof may be utilized. See U.S. Pat. Nos. 4,956,122; 4,827,064; and 4,827,073.

The number average molecular weights of the PAOs, which are known materials and generally available on a major commercial scale from suppliers such as ExxonMobil Chemical Company, Chevron Phillips Chemical Company, BP, and others, typically vary from 250 to 3,000, although PAO's may be made in viscosities up to 100 cSt (100° C.). The PAOs are typically comprised of relatively low molecular weight hydrogenated polymers or oligomers of alphaolefins which include, but are not limited to, C₂ to C₃₂ alphaolefins with the C₈ to C₁₆ alphaolefins, such as 1-hexene, 1-octene, 1-decene, 1-dodecene and the like, being preferred. The preferred polyalphaolefins are poly-1-hexene, poly-1-octene, poly-1-decene and poly-1-dodecene and mixtures thereof and mixed olefin-derived polyolefins. However, the dimers of higher olefins in the range of C₁₄ to C₁₈ may be used to provide low viscosity base stocks of acceptably low volatility. Depending on the viscosity grade and the starting oligomer, the PAOs may be predominantly trimers and tetramers of the starting olefins, with minor amounts of the higher oligomers, having a viscosity range of 1.5 to 12 cSt. PAO fluids of particular use may include 3.0 cSt, 3.4 cSt, and/or 3.6 cSt and combinations thereof. Bi-modal mixtures of PAO fluids having a viscosity range of 1.5 to 100 cSt may be used if desired.

The PAO fluids may be conveniently made by the polymerization of an alphaolefin in the presence of a polymerization catalyst such as the Friedel-Crafts catalysts including, for example, aluminum trichloride, boron trifluoride or complexes of boron trifluoride with water, alcohols such as ethanol, propanol or butanol, carboxylic acids or esters such as ethyl acetate or ethyl propionate. For example the methods disclosed by U.S. Pat. No. 4,149,178 or 3,382,291 may be conveniently used herein. Other descriptions of PAO synthesis are found in the following U.S. Pat. Nos. 3,742,082; 3,769,363; 3,876,720; 4,239,930; 4,367,352; 4,413,156; 4,434,408; 4,910,355; 4,956,122; and 5,068,487. The dimers of the C₁₄ to C₁₈ olefins are described in U.S. Pat. No. 4,218,330.

Other useful lubricant oil base stocks include wax isomerate base stocks and base oils, comprising hydroisomerized waxy stocks (e.g. waxy stocks such as gas oils, slack waxes, fuels hydrocracker bottoms, etc.), hydroisomerized Fischer-Tropsch waxes, Gas-to-Liquids (GTL) base stocks and base oils, and other wax isomerate hydroisomerized base stocks and base oils, or mixtures thereof Fischer-Tropsch waxes, the high boiling point residues of Fischer-Tropsch synthesis, are highly paraffinic hydrocarbons with very low sulfur content. The hydroprocessing used for the production of such base stocks may use an amorphous hydrocracking/hydroisomerization catalyst, such as one of the specialized lube hydrocracking (LHDC) catalysts or a crystalline hydrocracking/hydroisomerization catalyst, preferably a zeolitic catalyst. For example, one useful catalyst is ZSM-48 as described in U.S. Pat. No. 5,075,269, the disclosure of which is incorporated herein by reference in its entirety. Processes for making hydrocracked/hydroisomerized distillates and hydrocracked/hydroisomerized waxes are described, for example, in U.S. Pat. Nos. 2,817,693; 4,975,177; 4,921,594 and 4,897,178 as well as in British Patent Nos. 1,429,494; 1,350,257; 1,440,230 and 1,390,359. Each of the aforementioned patents is incorporated herein in their entirety. Particularly favorable processes are described in European Patent Application Nos. 464546 and 464547, also incorporated herein by reference. Processes using Fischer-Tropsch wax feeds are described in U.S. Pat. Nos. 4,594,172 and 4,943,672, the disclosures of which are incorporated herein by reference in their entirety.

Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized (wax isomerate) base oils be advantageously used in the instant disclosure, and may have useful kinematic viscosities at 100° C. of 3 cSt to 50 cSt, preferably 3 cSt to 30 cSt, more preferably 3.5 cSt to 25 cSt, as exemplified by GTL 4 with kinematic viscosity of 4.0 cSt at 100° C. and a viscosity index of 141. These Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and other wax-derived hydroisomerized base oils may have useful pour points of −20° C. or lower, and under some conditions may have advantageous pour points of −25° C. or lower, with useful pour points of −30° C. to −40° C. or lower. Useful compositions of Gas-to-Liquids (GTL) base oils, Fischer-Tropsch wax derived base oils, and wax-derived hydroisomerized base oils are recited in U.S. Pat. Nos. 6,080,301; 6,090,989, and 6,165,949 for example, and are incorporated herein in their entirety by reference.

The hydrocarbyl aromatics can be used as base oil or base oil component and can be any hydrocarbyl molecule that contains at least 5% of its weight derived from an aromatic moiety such as a benzenoid moiety or naphthenoid moiety, or their derivatives. These hydrocarbyl aromatics include alkyl benzenes, alkyl naphthalenes, alkyl diphenyl oxides, alkyl naphthols, alkyl diphenyl sulfides, alkylated bis-phenol A, alkylated thiodiphenol, and the like. The aromatic can be mono-alkylated, dialkylated, polyalkylated, and the like. The aromatic can be mono- or poly-functionalized. The hydrocarbyl groups can also be comprised of mixtures of alkyl groups, alkenyl groups, alkynyl, cycloalkyl groups, cycloalkenyl groups and other related hydrocarbyl groups. The hydrocarbyl groups can range from C₆ up to C₆₀ with a range of C₈ to C₂₀ often being preferred. A mixture of hydrocarbyl groups is often preferred, and up to three such substituents may be present. The hydrocarbyl group can optionally contain sulfur, oxygen, and/or nitrogen containing substituents. The aromatic group can also be derived from natural (petroleum) sources, provided at least 5% of the molecule is comprised of an above-type aromatic moiety. Viscosities at 100° C. of approximately 3 cSt to 50 cSt are preferred, with viscosities of approximately 3.4 cSt to 20 cSt often being more preferred for the hydrocarbyl aromatic component. In one embodiment, an alkyl naphthalene where the alkyl group is primarily comprised of 1-hexadecene is used. Other alkylates of aromatics can be advantageously used. Naphthalene or methyl naphthalene, for example, can be alkylated with olefins such as octene, decene, dodecene, tetradecene or higher, mixtures of similar olefins, and the like. Useful concentrations of hydrocarbyl aromatic in a lubricant oil composition can be 2% to 25%, preferably 4% to 20%, and more preferably 4% to 15%, depending on the application.

Alkylated aromatics such as the hydrocarbyl aromatics of the present disclosure may be produced by well-known Friedel-Crafts alkylation of aromatic compounds. See Friedel-Crafts and Related Reactions, Olah, G. A. (ed.), Inter-science Publishers, New York, 1963. For example, an aromatic compound, such as benzene or naphthalene, is alkylated by an olefin, alkyl halide or alcohol in the presence of a Friedel-Crafts catalyst. See Friedel-Crafts and Related Reactions, Vol. 2, part 1, chapters 14, 17, and 18, See Olah, G. A. (ed.), Inter-science Publishers, New York, 1964. Many homogeneous or heterogeneous, solid catalysts are known to one skilled in the art. The choice of catalyst depends on the reactivity of the starting materials and product quality requirements. For example, strong acids such as AlCl₃, BF₃, or HF may be used. In some cases, milder catalysts such as FeCl₃ or SnCl₄ are preferred. Newer alkylation technology uses zeolites or solid super acids.

Esters comprise a useful base stock. Additive solvency and seal compatibility characteristics may be secured by the use of esters such as the esters of dibasic acids with monoalkanols and the polyol esters of monocarboxylic acids. Esters of the former type include, for example, the esters of dicarboxylic acids such as phthalic acid, succinic acid, alkyl succinic acid, alkenyl succinic acid, maleic acid, azelaic acid, suberic acid, sebacic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkyl malonic acid, alkenyl malonic acid, etc., with a variety of alcohols such as butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, etc. Specific examples of these types of esters include dibutyl adipate, di(2-ethylhexyl) sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, etc.

Particularly useful synthetic esters are those which are obtained by reacting one or more polyhydric alcohols, preferably the hindered polyols (such as the neopentyl polyols, e.g., neopentyl glycol, trimethylol ethane, 2-methyl-2-propyl-1,3-propanediol, trimethylol propane, pentaerythritol and dipentaerythritol) with alkanoic acids containing at least 4 carbon atoms, preferably C₅ to C₃₀ acids such as saturated straight chain fatty acids including caprylic acid, capric acid, lauric acid, myristic acid, palmitic acid, stearic acid, arachic acid, and behenic acid, or the corresponding branched chain fatty acids or unsaturated fatty acids such as oleic acid, or mixtures of any of these materials.

Suitable synthetic ester components include the esters of trimethylol propane (TMP), trimethylol butane, trimethylol ethane, pentaerythritol and/or dipentaerythritol with one or more monocarboxylic acids containing from 5 to 10 carbon atoms. These esters are widely available commercially, for example, the Mobil P-41 and P-51 esters of ExxonMobil Chemical Company.

Also useful are esters derived from renewable material such as coconut, palm, rapeseed, soy, sunflower and the like. These esters may be monoesters, di-esters, polyol esters, complex esters, or mixtures thereof. These esters are widely available commercially, for example, the Mobil P-51 ester of ExxonMobil Chemical Company. Engine oil formulations containing renewable esters may also be included in this disclosure.

Other useful fluids of lubricating viscosity include non-conventional or unconventional base stocks that have been processed, preferably catalytically, or synthesized to provide high performance lubrication characteristics.

Non-conventional or unconventional base stocks/base oils include one or more of a mixture of base stock(s) derived from one or more Gas-to-Liquids (GTL) materials, as well as isomerate/isodewaxate base stock(s) derived from natural wax or waxy feeds, mineral and or non-mineral oil waxy feed stocks such as slack waxes, natural waxes, and waxy stocks such as gas oils, waxy fuels hydrocracker bottoms, waxy raffinate, hydrocrackate, thermal crackates, or other mineral, mineral oil, or even non-petroleum oil derived waxy materials such as waxy materials received from coal liquefaction or shale oil, and mixtures of such base stocks.

GTL materials are materials that are derived via one or more synthesis, combination, transformation, rearrangement, and/or degradation/deconstructive processes from gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks such as hydrogen, carbon dioxide, carbon monoxide, water, methane, ethane, ethylene, acetylene, propane, propylene, propyne, butane, butylenes, and butynes. GTL base stocks and/or base oils are GTL materials of lubricating viscosity that are generally derived from hydrocarbons; for example, waxy synthesized hydrocarbons, that are themselves derived from simpler gaseous carbon-containing compounds, hydrogen-containing compounds and/or elements as feed stocks. GTL base stock(s) and/or base oil(s) include oils boiling in the lube oil boiling range (1) separated/fractionated from synthesized GTL materials such as, for example, by distillation and subsequently subjected to a final wax processing step which involves either or both of a catalytic dewaxing process, or a solvent dewaxing process, to produce lube oils of reduced/low pour point; (2) synthesized wax isomerates, comprising, for example, hydrodewaxed or hydroisomerized cat and/or solvent dewaxed synthesized wax or waxy hydrocarbons; (3) hydrodewaxed or hydroisomerized cat and/or solvent dewaxed Fischer-Tropsch (F-T) material (i.e., hydrocarbons, waxy hydrocarbons, waxes and possible analogous oxygenates); preferably hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxing dewaxed F-T waxy hydrocarbons, or hydrodewaxed or hydroisomerized/followed by cat (or solvent) dewaxing dewaxed, F-T waxes, or mixtures thereof.

GTL base stock(s) and/or base oil(s) derived from GTL materials, especially, hydrodewaxed or hydroisomerized/followed by cat and/or solvent dewaxed wax or waxy feed, preferably F-T material derived base stock(s) and/or base oil(s), are characterized typically as having kinematic viscosities at 100° C. of from 2 mm²/s to 50 mm²/s (ASTM D445). They are further characterized typically as having pour points of −5° C. to −40° C. or lower (ASTM D97). They are also characterized typically as having viscosity indices of 80 to 140 or greater (ASTM D2270).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorus and aromatics make this materially especially suitable for the formulation of low SAP products.

The term GTL base stock and/or base oil and/or wax isomerate base stock and/or base oil is to be understood as embracing individual fractions of such materials of wide viscosity range as recovered in the production process, mixtures of two or more of such fractions, as well as mixtures of one or two or more low viscosity fractions with one, two or more higher viscosity fractions to produce a blend wherein the blend exhibits a target kinematic viscosity.

The GTL material, from which the GTL base stock(s) and/or base oil(s) is/are derived is preferably an F-T material (i.e., hydrocarbons, waxy hydrocarbons, wax).

In addition, the GTL base stock(s) and/or base oil(s) are typically highly paraffinic (>90% saturates), and may contain mixtures of monocycloparaffins and multicycloparaffins in combination with non-cyclic isoparaffins. The ratio of the naphthenic (i.e., cycloparaffin) content in such combinations varies with the catalyst and temperature used. Further, GTL base stock(s) and/or base oil(s) and hydrodewaxed, or hydroisomerized/cat (and/or solvent) dewaxed base stock(s) and/or base oil(s) typically have very low sulfur and nitrogen content, generally containing less than 10 ppm, and more typically less than 5 ppm of each of these elements. The sulfur and nitrogen content of GTL base stock(s) and/or base oil(s) obtained from F-T material, especially F-T wax, is essentially nil. In addition, the absence of phosphorus and aromatics make this material especially suitable for the formulation of low sulfur, sulfated ash, and phosphorus (low SAP) products.

Base oils for use in the formulated lubricating oils useful in the present disclosure are any of the variety of oils corresponding to API Group I, Group II, Group III, Group IV, and Group V oils and mixtures thereof, preferably API Group II, Group III, Group IV, and Group V oils and mixtures thereof, more preferably the Group III to Group V base oils due to their exceptional volatility, stability, viscometric and cleanliness features. Minor quantities of Group I stock, such as the amount used to dilute additives for blending into formulated lube oil products, can be tolerated but should be kept to a minimum, i.e. amounts only associated with their use as diluent/carrier oil for additives used on an “as-received” basis. Even in regard to the Group II stocks, it is preferred that the Group II stock be in the higher quality range associated with that stock, i.e. a Group II stock having a viscosity index in the range 100<VI<120.

The inventive base oils or base stocks described above have a kinematic viscosity, according to ASTM standards, of 2.5 cSt to 12 cSt (or mm²/s) at 100° C., preferably of 2.5 cSt to 9 cSt (or mm²/s) at 100° C., more preferably of 4 cSt to 8 cSt (or mm²/s) at 100° C., and even more preferably of 4 cSt to 6 cSt (or mm²/s) at 100° C.

Viscosity Modifiers

The lubricating engine oils of the instant disclosure include at least one viscosity modifier (also known as viscosity index improvers, VI improvers, and viscosity improvers) as part of the formulated oil. The at least one viscosity modifier may be included in the formulated engine oil at from 5 to 22 wt %, or 7 to 20 wt %, or 9 to 18 wt %, or 11 to 16 wt %, or 13 to 14 wt % based on the total weight of the engine oil.

Viscosity modifiers provide lubricants with high and low temperature operability. These additives impart shear stability at elevated temperatures and acceptable viscosity at low temperatures.

Suitable viscosity modifiers include high molecular weight hydrocarbons, polyesters and viscosity index improver dispersants that function as both a viscosity index improver and a dispersant. Typical molecular weights of these polymers are between 10,000 to 1,500,000, more typically 20,000 to 1,200,000, and even more typically between 50,000 and 1,000,000.

Examples of suitable viscosity modifiers are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, or alkylated styrenes. Polyisobutylene is a commonly used viscosity modifier. Another suitable viscosity modifier is polymethacrylate (copolymers of various chain length alkyl methacrylates, for example), some formulations of which also serve as pour point depressants. Other suitable viscosity modifiers include copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, and polyacrylates (copolymers of various chain length acrylates, for example). Specific examples include styrene-isoprene or styrene-butadiene based polymers of 50,000 to 200,000 molecular weight.

Olefin copolymers, are commercially available from Chevron Oronite Company LLC under the trade designation “PARATONE®” (such as “PARATONE® 8921” and “PARATONE® 8941”); from Afton Chemical Corporation under the trade designation “HiTEC®” (such as “HiTEC® 5850B”; and from The Lubrizol Corporation under the trade designation “Lubrizol® 7067C”. Polyisoprene polymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV200”; diene-styrene copolymers are commercially available from Infineum International Limited, e.g. under the trade designation “SV 260”.

Particularly advantageous viscosity modifiers of the lubricating engine oils of the instant disclosure are linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, alkylated styrenes or combinations thereof. Other particularly advantageous viscosity modifiers of the lubricating engine oils of the instant disclosure are polyisobutylene, polymethacrylate, polyisoprene, copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, styrene-butadiene based polymers, star polyisoprene polymers, star polyisoprene-styrene copolymers and combinations thereof. In one particularly preferred lubricating engine oil of the instant disclosure, the at least one viscosity modifier is a styrene isoprene copolymer having a molecular weight of from 50,000 to 200,000.

Viscosity modifiers are typically added as concentrates to the lubricating oil, in large amounts of diluent oil.

Other Additives

The formulated lubricating oil useful in the present disclosure may additionally contain one or more of the other commonly used lubricating oil performance additives including but not limited to antiwear agents, dispersants, detergents, friction modifiers, organic metallic friction modifiers, corrosion inhibitors, rust inhibitors, metal deactivators, extreme pressure additives, anti-seizure agents, wax modifiers, fluid-loss additives, seal compatibility agents, lubricity agents, anti-staining agents, chromophoric agents, defoamants, demulsifiers, emulsifiers, densifiers, wetting agents, gelling agents, tackiness agents, colorants, and others. For a review of many commonly used additives, see Klamann in Lubricants and Related Products, Verlag Chemie, Deerfield Beach, Fla.; ISBN 0-89573-177-0. Reference is also made to “Lubricant Additives” by M. W. Ranney, published by Noyes Data Corporation of Parkridge, N J (1973); see also U.S. Pat. No. 7,704,930, the disclosure of which is incorporated herein in its entirety. These additives are commonly delivered with varying amounts of diluent oil that may range from 5 weight percent to 50 weight percent.

The types and quantities of performance additives used in combination with the instant disclosure in lubricant compositions are not limited by the examples shown herein as illustrations.

Friction Modifiers

A friction modifier is any material or materials that can alter the coefficient of friction of a surface lubricated by any lubricant or fluid containing such material(s). Friction modifiers, also known as friction reducers, or lubricity agents or oiliness agents, and other such agents that change the ability of base oils, formulated lubricant compositions, or functional fluids, to modify the coefficient of friction of a lubricated surface may be effectively used in combination with the base oils or lubricant compositions of the present disclosure if desired. Friction modifiers that lower the coefficient of friction are particularly advantageous in combination with the base oils and lube compositions of this disclosure.

Illustrative friction modifiers may include, for example, organometallic compounds or materials, or mixtures thereof. Illustrative organometallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like, and mixtures thereof. Similar tungsten based compounds may be preferable.

Other illustrative friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, alkoxylated fatty acid esters, alkanolamides, polyol fatty acid esters, borated glycerol fatty acid esters, fatty alcohol ethers, and mixtures thereof.

Illustrative alkoxylated fatty acid esters include, for example, polyoxyethylene stearate, fatty acid polyglycol ester, and the like. These can include polyoxypropylene stearate, polyoxybutylene stearate, polyoxyethylene isosterate, polyoxypropylene isostearate, polyoxyethylene palmitate, and the like.

Illustrative alkanolamides include, for example, lauric acid diethylalkanolamide, palmic acid diethylalkanolamide, and the like. These can include oleic acid diethyalkanolamide, stearic acid diethylalkanolamide, oleic acid diethylalkanolamide, polyethoxylated hydrocarbylamides, polypropoxylated hydrocarbylamides, and the like.

Illustrative polyol fatty acid esters include, for example, glycerol mono-oleate, saturated mono-, di-, and tri-glyceride esters, glycerol mono-stearate, and the like. These can include polyol esters, hydroxyl-containing polyol esters, and the like.

Illustrative borated glycerol fatty acid esters include, for example, borated glycerol mono-oleate, borated saturated mono-, di-, and tri-glyceride esters, borated glycerol mono-sterate, and the like. In addition to glycerol polyols, these can include trimethylolpropane, pentaerythritol, sorbitan, and the like. These esters can be polyol monocarboxylate esters, polyol dicarboxylate esters, and on occasion polyoltricarboxylate esters. Preferred can be the glycerol mono-oleates, glycerol dioleates, glycerol trioleates, glycerol monostearates, glycerol distearates, and glycerol tristearates and the corresponding glycerol monopalmitates, glycerol dipalmitates, and glycerol tripalmitates, and the respective isostearates, linoleates, and the like. On occasion the glycerol esters can be preferred as well as mixtures containing any of these. Ethoxylated, propoxylated, butoxylated fatty acid esters of polyols, especially using glycerol as underlying polyol can be preferred.

Illustrative fatty alcohol ethers include, for example, stearyl ether, myristyl ether, and the like. Alcohols, including those that have carbon numbers from C₃ to C₅₀, can be ethoxylated, propoxylated, or butoxylated to form the corresponding fatty alkyl ethers. The underlying alcohol portion can preferably be stearyl, myristyl, C₁₁-C₁₃ hydrocarbon, oleyl, isosteryl, and the like.

The lubricating oils of this disclosure exhibit desired properties, e.g., wear control, in the presence or absence of a friction modifier.

Useful concentrations of friction modifiers may range from 0.01 weight percent to 5 weight percent, or about 0.1 weight percent to about 2.5 weight percent, or about 0.1 weight percent to about 1.5 weight percent, or about 0.1 weight percent to about 1 weight percent. Concentrations of molybdenum-containing materials are often described in terms of Mo metal concentration. Advantageous concentrations of Mo may range from 25 ppm to 700 ppm or more, and often with a preferred range of 50-200 ppm. Friction modifiers of all types may be used alone or in mixtures with the materials of this disclosure. Often mixtures of two or more friction modifiers, or mixtures of friction modifier(s) with alternate surface active material(s), are also desirable.

In addition to the friction modifiers described above, organic metallic friction modifiers may also be used in the lubricating engine oil formulations of this disclosure.

Illustrative organic metallic friction modifiers useful in the lubricating engine oil formulations of this disclosure include, for example, molybdenum amine, molybdenum diamine, an organotungstenate, a molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates, and the like. Similar tungsten based compounds may be preferable. Useful concentrations of the organic metallic friction modifiers may range from 0.01 weight percent to 5 weight percent, or 0.1 weight percent to 2.5 weight percent. Useful concentration of molybdenum can range from 25 to 700 ppm, or more preferably from 50 to 200 ppm.

Organic molybdenum containing friction modifiers are particularly preferred for the friction modifier mixture of the lubricating oils and the method for improving fuel efficiency and reducing frictional properties, while maintaining or improving deposit control, in an engine lubricated with a lubricating oil of the instant disclosure. The organic molybdenum containing friction modifier is selected from the group consisting of trimeric molybdenum carbamate, moly amine moly ester, molybdenum amine, molybdenum diamine, molybdenum dithiocarbamate, molybdenum dithiophosphates, molybdenum amine complexes, molybdenum carboxylates and combinations thereof. The organic molybdenum containing friction modifier in the friction modifier mixture contributes elemental molybdenum to the lubricating engine oil that yields an elemental molybdenum level in the lubricating engine oil of from 80 to 500 ppm, or 100 to 490 ppm, or 150 to 485 ppm, or 200 to 480 ppm, or 220 to 460 ppm, or 240 to 440 ppm, or 260 to 420 ppm, or 280 to 400 ppm, or 300 to 380 ppm, or 320 to 360 ppm of the lubricating engine oil.

Antiwear Additive

A metal alkylthiophosphate and more particularly a metal dialkyl dithio phosphate in which the metal constituent is zinc, or zinc dialkyl dithio phosphate (ZDDP) is a useful component of the lubricating oils of this disclosure. ZDDP can be derived from primary alcohols, secondary alcohols or mixtures thereof. ZDDP compounds generally are of the formula Zn[SP(S)(OR¹)(OR²)]₂ where R¹ and R² are C₁-C₁₈ alkyl groups, preferably C₂-C₁₂ alkyl groups. These alkyl groups may be straight chain or branched. Alcohols used in the ZDDP can be 2-propanol, butanol, secondary butanol, pentanols, hexanols such as 4-methyl-2-pentanol, n-hexanol, n-octanol, 2-ethyl hexanol, alkylated phenols, and the like. Mixtures of secondary alcohols or of primary and secondary alcohol can be preferred. Alkyl aryl groups may also be used.

Preferable zinc dithiophosphates which are commercially available include secondary zinc dithiophosphates such as those available from for example, The Lubrizol Corporation under the trade designations “LZ 677A”, “LZ 1095” and “LZ 1371”, from for example Chevron Oronite under the trade designation “OLOA 262” and from for example Afton Chemical under the trade designation “HITEC 7169”.

The ZDDP is typically used in amounts of from 0.4 weight percent to 1.2 weight percent, preferably from 0.5 weight percent to 1.0 weight percent, and more preferably from 0.6 weight percent to 0.8 weight percent, based on the total weight of the lubricating oil, although more or less can often be used advantageously. Preferably, the ZDDP is a secondary ZDDP and present in an amount of from 0.6 to 1.0 weight percent of the total weight of the lubricating oil.

In another form, the zinc dialkyl dithio phosphate (ZDDP) anti-wear additive may be included in the lubricating oil at from 0 to 1.1 wt. %, or 0.1 to 1.0 wt. %, or 0.2 to 0.9 wt. %, or 0.3 to 0.8 wt. %, or 0.4 to 0.7 wt. % of the lubricating engine oil. In this form, the elemental phosphorus level in the lubricating engine oil may range from 0 to 760 ppm, or 100 to 600 ppm, or 150 to 550 ppm, or 200 to 500 ppm, or 250 to 450 ppm, or 300 to 400 ppm of the lubricating engine oil.

Low phosphorus engine oil formulations are included in this disclosure. For such formulations, the phosphorus content is typically less than 0.12 weight percent preferably less than 0.10 weight percent and most preferably less than 0.085 weight percent. Low phosphorus can be preferred in combination with the friction modifier mixture.

Detergents

Illustrative detergents useful in this disclosure include, for example, alkali metal detergents, alkaline earth metal detergents, or mixtures of one or more alkali metal detergents and one or more alkaline earth metal detergents. A typical detergent is an anionic material that contains a long chain hydrophobic portion of the molecule and a smaller anionic or oleophobic hydrophilic portion of the molecule. The anionic portion of the detergent is typically derived from an organic acid such as a sulfur acid, carboxylic acid, phosphorus acid, phenol, or mixtures thereof. The counterion is typically an alkaline earth or alkali metal.

Salts that contain a substantially stochiometric amount of the metal are described as neutral salts and have a total base number (TBN, as measured by ASTM D2896) of from 0 to 80. Many compositions are overbased, containing large amounts of a metal base that is achieved by reacting an excess of a metal compound (a metal hydroxide or oxide, for example) with an acidic gas (such as carbon dioxide). Useful detergents can be neutral, mildly overbased, or highly overbased. These detergents can be used in mixtures of neutral, overbased, highly overbased calcium salicylate, sulfonates, phenates and/or magnesium salicylate, sulfonates, phenates. The TBN ranges can vary from low, medium to high TBN products, including as low as 0 to as high as 600. Mixtures of low, medium, high TBN can be used, along with mixtures of calcium and magnesium metal based detergents, and including sulfonates, phenates, salicylates, and carboxylates. A detergent mixture with a metal ratio of 1, in conjunction of a detergent with a metal ratio of 2, and as high as a detergent with a metal ratio of 5, can be used. Borated detergents can also be used.

Alkaline earth phenates are another useful class of detergent. These detergents can be made by reacting alkaline earth metal hydroxide or oxide (CaO, Ca(OH)₂, BaO, Ba(OH)₂, MgO, Mg(OH)₂, for example) with an alkyl phenol or sulfurized alkylphenol. Useful alkyl groups include straight chain or branched C₁-C₃₀ alkyl groups, preferably, C₄-C₂₀ or mixtures thereof. Examples of suitable phenols include isobutylphenol, 2-ethylhexylphenol, nonylphenol, dodecyl phenol, and the like. It should be noted that starting alkylphenols may contain more than one alkyl substituent that are each independently straight chain or branched and can be used from 0.5 to 6 weight percent. When a non-sulfurized alkylphenol is used, the sulfurized product may be obtained by methods well known in the art. These methods include heating a mixture of alkylphenol and sulfurizing agent (including elemental sulfur, sulfur halides such as sulfur dichloride, and the like) and then reacting the sulfurized phenol with an alkaline earth metal base.

Metal salts of carboxylic acids are also useful as detergents. These carboxylic acid detergents may be prepared by reacting a basic metal compound with at least one carboxylic acid and removing free water from the reaction product. These compounds may be overbased to produce the desired TBN level. Detergents made from salicylic acid are one preferred class of detergents derived from carboxylic acids. Useful salicylates include long chain alkyl salicylates. One useful family of compositions is of the formula

where R is an alkyl group having 1 to 30 carbon atoms, n is an integer from 1 to 4, and M is an alkaline earth metal. Preferred R groups are alkyl chains of at least C₁₁, preferably C₁₃ or greater. R may be optionally substituted with substituents that do not interfere with the detergent's function. M is preferably, calcium, magnesium, or barium. More preferably, M is calcium.

Hydrocarbyl-substituted salicylic acids may be prepared from phenols by the Kolbe reaction (see U.S. Pat. No. 3,595,791). The metal salts of the hydrocarbyl-substituted salicylic acids may be prepared by double decomposition of a metal salt in a polar solvent such as water or alcohol.

Alkaline earth metal phosphates are also used as detergents and are known in the art.

Detergents may be simple detergents or what is known as hybrid or complex detergents. The latter detergents can provide the properties of two detergents without the need to blend separate materials. See U.S. Pat. No. 6,034,039.

Preferred detergents include calcium phenates, calcium sulfonates, calcium salicylates, magnesium phenates, magnesium sulfonates, magnesium salicylates and other related components (including borated detergents), and mixtures thereof. Preferred mixtures of detergents include magnesium sulfonate and calcium salicylate, magnesium sulfonate and calcium sulfonate, magnesium sulfonate and calcium phenate, calcium phenate and calcium salicylate, calcium phenate and calcium sulfonate, calcium phenate and magnesium salicylate, calcium phenate and magnesium phenate.

The detergent concentration in the lubricating oils of this disclosure can range from 1.0 to 6.0 weight percent, preferably 2.0 to 5.0 weight percent, and more preferably from 2.0 weight percent to 4.0 weight percent, based on the total weight of the lubricating oil.

One particularly preferred detergent for the inventive lubricating engine oil and the inventive method for improving fuel efficiency, frictional properties and deposit control is an overbased calcium salicylate detergent and a magnesium sulfonate or a calcium sulfonate detergent. The overbased calcium salicylate detergent may be included in the formulated oil at from 0.5 to 2.5 wt %, or 1.0 to 2.0 wt %, or 1.2 to 1.8 wt %. The magnesium sulfonate or a calcium sulfonate detergent may also be included in the formulated oil at from 0.5 to 2.5 wt %, or 1.0 to 2.0 wt %, or 1.2 to 1.8 wt %. The overbased calcium salicylate detergent may also be included in the formulated oil such that it contributes elemental calcium based on the weight of the lubricating engine oil of from 200 ppm to 2000 ppm, or 300 to 1900 ppm, or 400 to 1800 ppm, or 500 to 1600 ppm, or 600 to 1500 ppm, or 700 to 1400 ppm, or 800 to 1300 ppm, or 900 to 1200 ppm.

In another form of this disclosure, mixtures of an overbased calcium salicylate detergent and a magnesium sulfonate or a calcium sulfonate detergent provide for advantageous lubricating engine oils and advantageous methods for improving fuel efficiency, frictional properties and deposit control. The magnesium sulfonate or a calcium sulfonate detergent may also be included in the formulated oil at from 0.5 to 2.5 wt %, or 1.0 to 2.0 wt %, or 1.2 to 1.8 wt %.

As used herein, the detergent concentrations are given on an “as delivered” basis. Typically, the active detergent is delivered with a process oil. The “as delivered” detergent typically contains from 20 weight percent to 80 weight percent, or from 40 weight percent to 60 weight percent, of active detergent in the “as delivered” detergent product.

Dispersants

During engine operation, oil-insoluble oxidation byproducts are produced. Dispersants help keep these byproducts in solution, thus diminishing their deposition on metal surfaces. Dispersants used in the formulation of the lubricating oil may be ashless or ash-forming in nature. Preferably, the dispersant is ashless. So-called ashless dispersants are organic materials that form substantially no ash upon combustion. For example, non-metal-containing or borated metal-free dispersants are considered ashless. In contrast, metal-containing detergents discussed above form ash upon combustion.

Suitable dispersants typically contain a polar group attached to a relatively high molecular weight hydrocarbon chain. The polar group typically contains at least one element of nitrogen, oxygen, or phosphorus. Typical hydrocarbon chains contain 50 to 400 carbon atoms.

A particularly useful class of dispersants are the alkenylsuccinic derivatives, typically produced by the reaction of a long chain hydrocarbyl substituted succinic compound, usually a hydrocarbyl substituted succinic anhydride, with a polyhydroxy or polyamino compound. The long chain hydrocarbyl group constituting the oleophilic portion of the molecule which confers solubility in the oil, is normally a polyisobutylene group. Many examples of this type of dispersant are well known commercially and in the literature. Exemplary U.S. patents describing such dispersants are U.S. Pat. Nos. 3,172,892; 3,215,707; 3,219,666; 3,316,177; 3,341,542; 3,444,170; 3,454,607; 3,541,012; 3,630,904; 3,632,511; 3,787,374 and 4,234,435. Other types of dispersant are described in U.S. Pat. Nos. 3,036,003; 3,200,107; 3,254,025; 3,275,554; 3,438,757; 3,454,555; 3,565,804; 3,413,347; 3,697,574; 3,725,277; 3,725,480; 3,726,882; 4,454,059; 3,329,658; 3,449,250; 3,519,565; 3,666,730; 3,687,849; 3,702,300; 4,100,082; 5,705,458. A further description of dispersants may be found, for example, in European Patent Application No. 471 071, to which reference is made for this purpose.

Hydrocarbyl-substituted succinic acid and hydrocarbyl-substituted succinic anhydride derivatives are useful dispersants. In particular, succinimide, succinate esters, or succinate ester amides prepared by the reaction of a hydrocarbon-substituted succinic acid compound preferably having at least 50 carbon atoms in the hydrocarbon substituent, with at least one equivalent of an alkylene amine are particularly useful, although on occasion, having a hydrocarbon substituent between 20-50 carbon atoms can be useful.

Succinimides are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and amines. Molar ratios can vary depending on the polyamine. For example, the molar ratio of hydrocarbyl substituted succinic anhydride to TEPA can vary from 1:1 to 5:1. Representative examples are shown in U.S. Pat. Nos. 3,087,936; 3,172,892; 3,219,666; 3,272,746; 3,322,670; and 3,652,616, 3,948,800; and Canada Patent No. 1,094,044.

Succinate esters are formed by the condensation reaction between hydrocarbyl substituted succinic anhydrides and alcohols or polyols. Molar ratios can vary depending on the alcohol or polyol used. For example, the condensation product of a hydrocarbyl substituted succinic anhydride and pentaerythritol is a useful dispersant.

Succinate ester amides are formed by condensation reaction between hydrocarbyl substituted succinic anhydrides and alkanol amines. For example, suitable alkanol amines include ethoxylated polyalkylpolyamines, propoxylated polyalkylpolyamines and polyalkenylpolyamines such as polyethylene polyamines. One example is propoxylated hexamethylenediamine. Representative examples are shown in U.S. Pat. No. 4,426,305.

The molecular weight of the hydrocarbyl substituted succinic anhydrides used in the preceding paragraphs will typically range between 800 and 2,500 or more. The above products can be post-reacted with various reagents such as sulfur, oxygen, formaldehyde, carboxylic acids such as oleic acid. The above products can also be post reacted with boron compounds such as boric acid, borate esters or highly borated dispersants, to form borated dispersants generally having from 0.1 to 5 moles of boron per mole of dispersant reaction product.

Mannich base dispersants are made from the reaction of alkylphenols, formaldehyde, and amines. See U.S. Pat. No. 4,767,551, which is incorporated herein by reference. Process aids and catalysts, such as oleic acid and sulfonic acids, can also be part of the reaction mixture. Molecular weights of the alkylphenols range from 800 to 2,500. Representative examples are shown in U.S. Pat. Nos. 3,697,574; 3,703,536; 3,704,308; 3,751,365; 3,756,953; 3,798,165; and 3,803,039.

Typical high molecular weight aliphatic acid modified Mannich condensation products useful in this disclosure can be prepared from high molecular weight alkyl-substituted hydroxyaromatics or HNR2 group-containing reactants.

Hydrocarbyl substituted amine ashless dispersant additives are well known to one skilled in the art; see, for example, U.S. Pat. Nos. 3,275,554; 3,438,757; 3,565,804; 3,755,433, 3,822,209, and 5,084,197.

Preferred dispersants include borated and non-borated succinimides, including those derivatives from mono-succinimides, bis-succinimides, and/or mixtures of mono- and bis-succinimides, wherein the hydrocarbyl succinimide is derived from a hydrocarbylene group such as polyisobutylene having a Mn of from 500 to 5000, or from 1000 to 3000, or 1000 to 2000, or a mixture of such hydrocarbylene groups, often with high terminal vinylic groups. Other preferred dispersants include succinic acid-esters and amides, alkylphenol-polyamine-coupled Mannich adducts, their capped derivatives, and other related components. Such additives may be used in an amount of 0.1 to 20 weight percent, preferably 0.5 to 8 weight percent, or more preferably 0.5 to 4 weight percent. On an active ingredient basis, such additives may be used in an amount of 0.06 to 14 weight percent, preferably 0.3 to 6 weight percent. The hydrocarbon portion of the dispersant atoms can range from C₆₀ to C₄₀₀, or from C₇₀ to C₃₀₀, or from C₇₀ to C₂₀₀. These dispersants may contain both neutral and basic nitrogen, and mixtures of both. Dispersants can be end-capped by borates and/or cyclic carbonates.

One particularly preferred dispersant for the inventive lubricating engine oil and the inventive method for improving fuel efficiency, frictional properties and deposit control is a non-borated polyisobutenyl bis-succinimide (PIBSA) dispersant. The non-borated PIBSA dispersant may be included in the formulated oil at from 2.0 to 6.0 wt %, or 3.0 to 5.0 wt %, or 3.5 to 4.5 wt %.

As used herein, the dispersant concentrations are given on an “as delivered” basis. Typically, the active dispersant is delivered with a process oil. The “as delivered” dispersant typically contains from 20 weight percent to 80 weight percent, or from 40 weight percent to 60 weight percent, of active dispersant in the “as delivered” dispersant product.

Antioxidants

Antioxidants retard the oxidative degradation of base oils during service. Such degradation may result in deposits on metal surfaces, the presence of sludge, or a viscosity increase in the lubricant. One skilled in the art knows a wide variety of oxidation inhibitors that are useful in lubricating oil compositions. See, Klamann in Lubricants and Related Products, op cite, and U.S. Pat. Nos. 4,798,684 and 5,084,197, for example.

Useful antioxidants include hindered phenols. These phenolic antioxidants may be ashless (metal-free) phenolic compounds or neutral or basic metal salts of certain phenolic compounds. Typical phenolic antioxidant compounds are the hindered phenolics which are the ones which contain a sterically hindered hydroxyl group, and these include those derivatives of dihydroxy aryl compounds in which the hydroxyl groups are in the o- or p-position to each other. Typical phenolic antioxidants include the hindered phenols substituted with C₆+ alkyl groups and the alkylene coupled derivatives of these hindered phenols. Examples of phenolic materials of this type 2-t-butyl-4-heptyl phenol; 2-t-butyl-4-octyl phenol; 2-t-butyl-4-dodecyl phenol; 2,6-di-t-butyl-4-heptyl phenol; 2,6-di-t-butyl-4-dodecyl phenol; 2-methyl-6-t-butyl-4-heptyl phenol; and 2-methyl-6-t-butyl-4-dodecyl phenol. Other useful hindered mono-phenolic antioxidants may include for example hindered 2,6-di-alkyl-phenolic proprionic ester derivatives. Bis-phenolic antioxidants may also be advantageously used in combination with the instant disclosure. Examples of ortho-coupled phenols include: 2,2′-bis(4-heptyl-6-t-butyl-phenol); 2,2′-bis(4-octyl-6-t-butyl-phenol); and 2,2′-bis(4-dodecyl-6-t-butyl-phenol). Para-coupled bisphenols include for example 4,4′-bis(2,6-di-t-butyl phenol) and 4,4′-methylene-bis(2,6-di-t-butyl phenol).

Effective amounts of one or more catalytic antioxidants may also be used. The catalytic antioxidants comprise an effective amount of a) one or more oil soluble polymetal organic compounds; and, effective amounts of b) one or more substituted N,N′-diaryl-o-phenylenediamine compounds or c) one or more hindered phenol compounds; or a combination of both b) and c). Catalytic antioxidants are more fully described in U.S. Pat. No. 8,048,833, herein incorporated by reference in its entirety.

Non-phenolic oxidation inhibitors which may be used include aromatic amine antioxidants and these may be used either as such or in combination with phenolics. Typical examples of non-phenolic antioxidants include: alkylated and non-alkylated aromatic amines such as aromatic monoamines of the formula R⁸R⁹R¹⁰N where R⁸ is an aliphatic, aromatic or substituted aromatic group, R⁹ is an aromatic or a substituted aromatic group, and R¹² is H, alkyl, aryl or R¹¹S(O)_(X)R¹² where R¹¹ is an alkylene, alkenylene, or aralkylene group, R¹² is a higher alkyl group, or an alkenyl, aryl, or alkaryl group, and x is 0, 1 or 2. The aliphatic group R⁸ may contain from 1 to 20 carbon atoms, and preferably contains from 6 to 12 carbon atoms. The aliphatic group is a saturated aliphatic group. Preferably, both R⁸ and R⁹ are aromatic or substituted aromatic groups, and the aromatic group may be a fused ring aromatic group such as naphthyl. Aromatic groups R⁸ and R⁹ may be joined together with other groups such as S.

Typical aromatic amines antioxidants have alkyl substituent groups of at least 6 carbon atoms. Examples of aliphatic groups include hexyl, heptyl, octyl, nonyl, and decyl. Generally, the aliphatic groups will not contain more than 14 carbon atoms. The general types of amine antioxidants useful in the present compositions include diphenylamines, phenyl naphthylamines, phenothiazines, imidodibenzyls and diphenyl phenylene diamines. Mixtures of two or more aromatic amines are also useful. Polymeric amine antioxidants can also be used. Particular examples of aromatic amine antioxidants useful in the present disclosure include: p,p′-dioctyldiphenylamine; t-octylphenyl-alpha-naphthylamine; phenyl-alphanaphthylamine; and p-octylphenyl-alpha-naphthylamine.

Sulfurized alkyl phenols and alkali or alkaline earth metal salts thereof also are useful antioxidants.

Preferred antioxidants include hindered phenols, arylamines. These antioxidants may be used individually by type or in combination with one another. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5 weight percent, more preferably zero to less than 1.5 weight percent, more preferably zero to less than 1 weight percent.

Pour Point Depressants (PPDs)

Conventional pour point depressants (also known as lube oil flow improvers) may be added to the compositions of the present disclosure if desired. These pour point depressant may be added to lubricating compositions of the present disclosure to lower the minimum temperature at which the fluid will flow or can be poured. Examples of suitable pour point depressants include polymethacrylates, polyacrylates, polyarylamides, condensation products of haloparaffin waxes and aromatic compounds, vinyl carboxylate polymers, and terpolymers of dialkylfumarates, vinyl esters of fatty acids and allyl vinyl ethers. U.S. Pat. Nos. 1,815,022; 2,015,748; 2,191,498; 2,387,501; 2,655, 479; 2,666,746; 2,721,877; 2,721,878; and 3,250,715 describe useful pour point depressants and/or the preparation thereof. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5 weight percent.

Seal Compatibility Agents

Seal compatibility agents help to swell elastomeric seals by causing a chemical reaction in the fluid or physical change in the elastomer. Suitable seal compatibility agents for lubricating oils include organic phosphates, alkoxysulfonlanes (C₁₀ alcohol, for example), aromatic esters, aromatic hydrocarbons, esters (butylbenzyl phthalate, for example), and polybutenyl succinic anhydride. Such additives may be used in an amount of 0.01 to 3 weight percent, preferably 0.01 to 2 weight percent.

Antifoam Agents

Antifoam agents may advantageously be added to lubricant compositions. These agents retard the formation of stable foams. Silicones and organic polymers are typical antifoam agents. For example, polysiloxanes, such as silicon oil or polydimethyl siloxane, provide antifoam properties. Antifoam agents are commercially available and may be used in conventional minor amounts along with other additives such as demulsifiers; usually the amount of these additives combined is less than 1 weight percent and often less than 0.1 weight percent.

Inhibitors and Antirust Additives

Antirust additives (or corrosion inhibitors) are additives that protect lubricated metal surfaces against chemical attack by water or other contaminants. A wide variety of these are commercially available.

One type of antirust additive is a polar compound that wets the metal surface preferentially, protecting it with a film of oil. Another type of antirust additive absorbs water by incorporating it in a water-in-oil emulsion so that only the oil touches the metal surface. Yet another type of antirust additive chemically adheres to the metal to produce a non-reactive surface. Examples of suitable additives include zinc dithiophosphates, metal phenolates, basic metal sulfonates, fatty acids and amines. Such additives may be used in an amount of 0.01 to 5 weight percent, preferably 0.01 to 1.5 weight percent.

When lubricating oil compositions contain one or more of the additives discussed above, the additive(s) are blended into the composition in an amount sufficient for it to perform its intended function. Typical amounts of such additives useful in the present disclosure are shown in Table 2 below.

It is noted that many of the additives are shipped from the additive manufacturer as a concentrate, containing one or more additives together, with a certain amount of base oil diluents. Accordingly, the weight amounts in the table below, as well as other amounts mentioned herein, are directed to the amount of active ingredient (that is the non-diluent portion of the ingredient). The weight percent (wt %) indicated below is based on the total weight of the lubricating oil composition.

TABLE 2 Typical Amounts of Other Lubricating Oil Components Approximate wt % Approximate wt % Compound (Useful) (Preferred) Dispersant  0.1-20 0.1-8  Detergent  0.1-20 0.1-8  Friction Modifier 0.01-5  0.01-1.5 Antioxidant 0.1-5  0.1-1.5 Pour Point Depressant 0.0-5 0.01-1.5 (PPD) Anti-foam Agent 0.001-3  0.001-0.15 Viscosity modifier (solid 0.1-2 0.1-1  polymer basis) Anti-wear 0.1-2 0.5-1  Inhibitor and Antirust 0.01-5  0.01-1.5

The foregoing additives are all commercially available materials. These additives may be added independently but are usually precombined in packages which can be obtained from suppliers of lubricant oil additives. Additive packages with a variety of ingredients, proportions and characteristics are available and selection of the appropriate package will take the requisite use of the ultimate composition into account.

The following non-limiting examples are provided to illustrate the disclosure.

EXAMPLES Example 1

Comparative and inventive lubricating engine oils were prepared according to the formulations shown in FIGS. 2-5. Formulation details are shown in weight percent based on the total weight percent of the formulation, of the various comparative and inventive formulations. FIG. 1 shows the various base stocks and the properties of the base stocks used in accordance with the lubricating engine oils of FIGS. 2-5. Seven different ester based Group V base stocks (second lubricating oil base stock) were evaluated in combination with a first lubricating oil base stock (GTL4, GTL8, PAO-4, PAO-6 or combinations thereof). The inventive and comparative lubricating engine oils also included at least one viscosity modifier. The five different viscosity modifiers (VM) evaluated either individually or in combination with one another were 1) a polymethacrylate comb VM, 2) a star VM containing styrene, 3) a styrene isoprene diblock VM solid polymer, 4) an isoprene star VM containing styrene in star arms and 5) an ethylene propylene OCP VM. The lubricating engine oils also included other lubricating oil additives, which were held constant in terms of compositional ingredients and weight loading (13.95 or 13.95 wt %) of the total lubricating engine oil. The SAE oil viscosity grade of all the lubricating engine oils were 0W-30 or 5W-30.

The comparative and inventive lubricating engine oils were bench tested or evaluated for Kinematic viscosity at 25, 40 and 100 deg. C. measured by ASTM D445, high temperature high shear viscosity at 150 deg. C. measured by ASTM D4683, thermo-oxidation engine oil simulation test (TEOST 33C deposits) measured by ASTM D6335, Viscosity Index as measured by ASTM D2270, and CCS viscosity at 25, 30 and 35 deg. C. as measured by D5293. The property results for the comparative and inventive lubricating engine oils are also depicted in FIGS. 2-5. All inventive examples were blended such that the D4683 High Temperature High Shear viscosity was 3.5 cP. This viscosity is a common requirement for many European auto-builders.

The bench test results of FIGS. 2-5 show that the inventive lubricating engine oils provide a low kinematic viscosity at 25 deg. C. as a measure of fuel efficiency improvement and a low TEOST 33C deposits as measure of deposit control improvement. In particular, the inventive lubricating engine oils of FIGS. 2-5 provide a novel combination of a kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt and a TEOST 33C total deposits of less than or equal to 60 mg. in comparison to the comparative lubricating engine oils. The inventive lubricating engine oils included a combination of from 20 to 85 wt % of a first lubricating oil base stock including a GTL, a PAO and combinations thereof; and from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock selected from the types shown in FIGS. 2-5; and from 5 to 20 wt % of at least one viscosity modifier selected from 1) a polymethacrylate comb VM, 2) a star VM containing styrene, 3) a styrene isoprene diblock VM solid polymer, 4) an isoprene star VM containing styrene in star arms and 5) an ethylene propylene OCP VM, and 6) combinations thereof. For the inventive lubricating engine oils, the improvements in fuel efficiencies as measured by KV at 25 deg. C. and deposit control as measured by TEOST 33C were surprising and unexpected relative to the prior art and the comparative lubricating engine oils.

Example 2

Comparative example 1 of FIG. 2 contains no Group V base stock and no viscosity modifier. This formulation had a KV25C of 140 cSt, which is expected to provide unacceptable NEDC/WLTP fuel economy performance. Comparative example 1 also failed to meet the D4683 target of 3.5 cP. Comparative examples 11, 13, and 14 use a star VM containing styrene, a star VM containing styrene in the arms, and an ethylene propylene OCP VM respectively. However, these formulations contain no Group V basestock. All three of these examples met the D4683 target of 3.5 cP. However, all three of these formulations failed to provide acceptable D6335 TEOST 33C deposit control. Thus, the inclusion of at least one VM and one Group V base stock was needed in each of the inventive examples of FIGS. 2-5. For each of the following seven ester based Group V base stocks (1=C11/C13/C15/C17 Estolide, 2=C8/C10 trimethylolpropane (TMP) ester, 3=C7/C9/C11/C13/C15 TMP ester, 4=C6/C7/C9 TMP ester, 5=C15/C17 propylene glycol diester, 6=C6/C7/C9 TMP ester, 7=C4/C5/C6/C7/C8/C9 TMP ester), four different lubricating engine oil formulations were evaluated (A-D in Table 3 below). Each formulation contained an identical additive system but used a combination of one of two ester treat rates (either 5% or 50% wt % based on the total lubricating oil) with either a styrene isoprene VM or a PMA VM. PMA VMs have been shown to improve fuel economy because they generate a desirable viscosity vs. temperature profile. Two formulations using PMA VMs were used as comparative benchmarks in this example. The ester treat rates in these formulations were 5 wt % (A) and 50 wt % (B) in combination with a PMA VM. Reference formulations (C) contained 5 wt % ester and two styrene isoprene VMs (1. styrene isoprene block copolymer and 2. isoprene star polymer containing styrene in the arms). The inventive lubricating engine oils of this Example contained 50% ester and replaced the PMA VM with the two styrene isoprene VMs indicated above. VM treat rates varied between 4.50 and 10.65 and were adjusted to target an HTHS 150° C. value of 3.5 as determined by ASTM D4683. The seven esters tested were labeled as Ester 1-7. Ester 1 is an Estolide ester, Ester 2-4 and 6-7 are TMP esters and Ester 5 is a diester. The four different combinations of VM/ester treat rate as shown below in Table 3 and are labeled A through D.

TABLE 3 Ester treat rate, % VM type A 5 PMA B 50 PMA C 5 Styrene isoprene D 50 Styrene isoprene

Therefore, each formulation was labeled with the ester used in the formulation (1-7) and the combination of VM type and ester treat rate (A-D). Each formulation was tested for turbocharger deposit control in ASTM D6335 TEOST 33C test and KV at 25° C. (which was used to rank the performance of the oils in NEDC and WLTP fuel economy tests). Having a KV 25° C.≤125 cSt is advantageous for fuel efficiency. In addition, TEOST 33C deposits of less than or equal to 60 mg is considered advantageous for engine cleanliness. For each ester, formulation A (5% ester+PMA VM) exhibited greater than 60 mg total deposits, while formulation D (50% ester+styrene isoprene VM) exhibited less than 60 mg deposits.

For each ester, formulation D (50% ester+styrene isoprene VM) showed a KV at 25° C. value between 78.6 and 107.8° C., which is expected to provide excellent performance in NEDC and WLTP fuel economy tests. Formulation A (5% ester+PMA VM) showed lower KV values resulting in higher FEI predictions. The reference formulations C (5% ester+styrene isoprene VM) exhibited KV@25° C. values ranging from 118.1 to 123.9° C. and thus are expected to provide acceptable results in NEDC and WLTP fuel economy tests.

All patents and patent applications, test procedures (such as ASTM methods, UL methods, and the like), and other documents cited herein are fully incorporated by reference to the extent such disclosure is not inconsistent with this disclosure and for all jurisdictions in which such incorporation is permitted.

When numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated. While the illustrative embodiments of the disclosure have been described with particularity, it will be understood that various other modifications will be apparent to and can be readily made by those skilled in the art without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the scope of the claims appended hereto be limited to the examples and descriptions set forth herein but rather that the claims be construed as encompassing all the features of patentable novelty which reside in the present disclosure, including all features which would be treated as equivalents thereof by those skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference to numerous embodiments and specific examples. Many variations will suggest themselves to those skilled in this art in light of the above detailed description. All such obvious variations are within the full intended scope of the appended claims. 

1. A method for improving fuel efficiency while maintaining or improving deposit control, in an engine lubricated with a lubricating oil by using as the lubricating engine oil a formulated oil, said formulated oil having a composition comprising: from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier, and wherein the remainder of the lubricating engine oil includes one or more other lubricating oil additives; wherein fuel efficiency properties are improved (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and deposit control is maintained or improved (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier.
 2. The method of claim 1, wherein the at least one viscosity modifier comprises linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, alkylated styrenes or combinations thereof.
 3. The method of claim 1, wherein the at least one viscosity modifier is selected from the group consisting of polyisobutylene, polymethacrylate, polyisoprene, copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, styrene-butadiene based polymers, star polyisoprene polymers, star polyisoprene-styrene copolymers and combinations thereof.
 4. The method of claim 3, wherein the at least one viscosity modifier is a styrene isoprene copolymer having a molecular weight of from 50,000 to 200,000.
 5. The method of claim 1, wherein the at least one ester based Group V base stock comprises an ester of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol or dipentaerythritol with one or more monocarboxylic acids containing from 5 to 20 carbon atoms.
 6. The method of claim 1, wherein the at least one ester based Group V base stock is selected from the group consisting of a C8/C10/C12/C14/C16/C18 Estolide ester, a C11/C13/C15/C17 Estolide ester, a C8/C10 trimethylolpropane (TMP) ester, a C6/C7/C8/C10 TMP ester, a C5/C6/C7/C8/C9/C10 TMP ester, a C8/C10/C12/C14/C16/C18/C20 TMP ester, a C7/C8/C10 TMP ester, a C7/C9/C11/C13/C15 TMP ester, a C6/C7/C9 TMP ester, a C6/C7/C9 TMP ester, a C4/C5/C6/C7/C8/C9 TMP ester, a C15/C17 propylene glycol diester, a C16/C18 propylene glycol diester and combinations thereof.
 7. The method of claim 6, where the at least one ester based Group V base stock comprises from 25 to 55 wt % of the lubricating engine oil.
 8. The method of claim 1, wherein the at least one ester based Group V base stock comprises a monoester, a di-ester, a polyol ester, a complex ester or mixtures thereof derived from a renewable biological material.
 9. The method of claim 8, wherein the renewable biological material is derived from coconut oil, palm oil, rapeseed oil, soy oil, vegetable oil, or sunflower oil.
 10. The method of claim 1, wherein the one or more other lubricating oil additives are selected from the group consisting of an anti-wear additive, antioxidant, detergents, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 11. The method of claim 1, wherein the lubricating engine oil has a kinematic viscosity at 25 deg. C. of less than or equal to 110 cSt.
 12. The method of claim 1, wherein the lubricating engine oil has TEOST 33C total deposits less than or equal to 50 mg.
 13. The method of claim 1, wherein the lubricating engine oil has a kinematic viscosity at 100 deg. C. ranging from 8 to 15 cSt.
 14. The method of claim 1, wherein the first lubricating oil base stock is a mixture of a Group III base stock and a Group IV base stock.
 15. The method of claim 14, wherein the Group III base stock is a gas to liquids (GTL) base stock and the Group IV base stock is a polyalphaolefin (PAO) base stock.
 16. The method of claim 15, wherein the GTL ranges from 20 to 75 wt % of the lubricating engine oil and the PAO ranges from 2 to 10 wt % of the lubricating engine oil.
 17. The method of claim 1, wherein the high temperature high shear (HTHS) viscosity at 150° C. of the lubricating engine oil ranges from 1.5 to 4.5 cP and wherein the lubricating engine oil is an SAE viscosity grade selected from the group consisting of 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.
 18. A lubricating engine oil having a composition comprising: from 20 to 85 wt % of a first lubricating oil base stock selected from the group consisting of a Group I base stock, a Group II base stock, a Group III base stock, a Group IV base stock, and combinations thereof; from 5 to 55 wt % of a second lubricating oil base stock comprising at least one ester based Group V base stock; from 5 to 20 wt % of at least one viscosity modifier, and wherein the remainder of the lubricating engine oil includes one or more other lubricating oil additives; wherein fuel efficiency properties are improved (kinematic viscosity at 25 deg. C. of less than or equal to 125 cSt) and deposit control is maintained or improved (TEOST 33C total deposits less than or equal to 60 mg) as compared to fuel efficiency properties and deposit control achieved using a lubricating engine oil not containing the at least one ester based Group V base stock and the at least one viscosity modifier.
 19. The lubricating engine oil of claim 18, wherein the at least one viscosity modifier comprises linear or star-shaped polymers and copolymers of methacrylate, butadiene, olefins, alkylated styrenes or combinations thereof.
 20. The lubricating engine oil of claim 18, wherein the at least one viscosity modifier is selected from the group consisting of polyisobutylene, polymethacrylate, polyisoprene, copolymers of ethylene and propylene, hydrogenated block copolymers of styrene and isoprene, styrene-butadiene based polymers, star polyisoprene polymers, star polyisoprene-styrene copolymers and combinations thereof.
 21. The lubricating engine oil of claim 20, wherein the at least one viscosity modifier is a styrene isoprene copolymer having a molecular weight of from 50,000 to 200,000.
 22. The lubricating engine oil of claim 18, wherein the at least one ester based Group V base stock comprises an ester of trimethylol propane, trimethylol butane, trimethylol ethane, pentaerythritol or dipentaerythritol with one or more monocarboxylic acids containing from 5 to 20 carbon atoms.
 23. The lubricating engine oil of claim 18, wherein the at least one ester based Group V base stock is selected from the group consisting of a C8/C10/C12/C14/C16/C18 Estolide ester, a C11/C13/C15/C17 Estolide ester, a C8/C10 trimethylolpropane (TMP) ester, a C6/C7/C8/C10 TMP ester, a C5/C6/C7/C8/C9/C10 TMP ester, a C8/C10/C12/C14/C16/C18/C20 TMP ester, a C7/C8/C10 TMP ester, a C7/C9/C11/C13/C15 TMP ester, a C6/C7/C9 TMP ester, a C6/C7/C9 TMP ester, a C4/C5/C6/C7/C8/C9 TMP ester, a C15/C17 propylene glycol diester, a C16/C18 propylene glycol diester and combinations thereof.
 24. The lubricating engine oil of claim 23, where the at least one ester based Group V base stock comprises from 25 to 55 wt % of the lubricating engine oil.
 25. The lubricating engine oil of claim 18, wherein the at least one ester based Group V base stock comprises a monoester, a di-ester, a polyol ester, a complex ester or mixtures thereof derived from a renewable biological material.
 26. The lubricating engine oil of claim 25, wherein the renewable biological material is derived from coconut oil, palm oil, rapeseed oil, soy oil, vegetable oil, or sunflower oil.
 27. The lubricating engine oil of claim 18, wherein the one or more other lubricating oil additives are selected from the group consisting of an anti-wear additive, antioxidant, detergents, dispersant, pour point depressant, corrosion inhibitor, metal deactivator, seal compatibility additive, anti-foam agent, inhibitor, anti-rust additive, and friction modifier.
 28. The lubricating engine oil of claim 18, wherein the lubricating engine oil has a kinematic viscosity at 25 deg. C. of less than or equal to 110 cSt.
 29. The lubricating engine oil of claim 18, wherein the lubricating engine oil has TEOST 33C total deposits less than or equal to 50 mg.
 30. The lubricating engine oil of claim 18, wherein the lubricating engine oil has a kinematic viscosity at 100 deg. C. ranging from 8 to 15 cSt.
 31. The lubricating engine oil of claim 18, wherein the first lubricating oil base stock is a mixture of a Group III base stock and a Group IV base stock.
 32. The lubricating engine oil of claim 31, wherein the Group III base stock is a gas to liquids (GTL) base stock and the Group IV base stock is a polyalphaolefin (PAO) base stock.
 33. The lubricating engine oil of claim 32, wherein the GTL ranges from 20 to 75 wt % of the lubricating engine oil and the PAO ranges from 2 to 10 wt % of the lubricating engine oil.
 34. The lubricating engine oil of claim 18, wherein the high temperature high shear (HTHS) viscosity at 150° C. of the lubricating engine oil ranges from 1.5 to 4.5 cP.
 35. The lubricating engine oil of claim 34, wherein the lubricating engine oil is an SAE viscosity grade selected from the group consisting of 0W-30, 5W-30, 0W-20, 5W-20, 0W-16, 5W-16, 0W-12, 5W-12, 0W-8, and 5W-8.
 36. The lubricating engine oil of claim 18, wherein the lubricating engine oil is a passenger vehicle engine oil (PVEO). 